This invention relates to ultra high-strength hydraulic cement compositions with significantly improved fluidity and workability adapted for use in the production of ultra high-strength concrete and mortar.
In order to produce high-strength concrete, it has been known to reduce the water-to-cement ratio and to make up for the resultant lowering of its fluidity by using a cement dispersion agent such as condensation products of naphthalene sulfonic acid and formaldehyde, condensation products of melamine sulfonic acid and formaldehyde or water-soluble vinyl copolymers (U.S. Pat. No. 4,962,173 and Japanese Patent Application Tokkai 3-93660). For the purpose of production of high-strength concrete, it has also been known to reduce the water-to-cement ratio and to use a microscopic powder admixture such as silica fume or blast-furnace slag in addition to cement (Japanese Patent Publications Tokko 60-59182 and Tokkai 3-93660).
If such a prior art method is used for the production of an ultra high-strength hydraulic cement composition from which high quality ultra high-strength hardened concrete with compressive strength greater than 1100kgf/cm.sup.2 can be obtained by keeping the water-to-cement ratio extremely low, however, it is not possible to obtain sufficiently large fluidity, and the drop in its fluidity with the passage of time after the mixing (hereinafter referred to as the slump loss) is significantly large. In other words, only compositions with poor fluidity and workability, having no practical use, can be obtained.